A rigorous examination of health care claims data can help to guide states and local health- care systems to understand the quality, costs and outcomes of cancer care. Until recently, broad population-based data on cancer care have been available primarily through the SEER- Medicare database, which only includes individuals in fee-for-service Medicare. State All-Payer Claims Databases (APCDs) offer a novel and comprehensive source of utilization and cost data, but lack clinical detail. State cancer registries, in contrast, contain key clinical information on cancer histology, stage, and dates of diagnosis but lack detailed utilization or cost data. Therefore, this project will link the Massachusetts APCD to the Massachusetts Cancer Registry (MCR) for adults diagnosed with lung, colorectal, breast, or prostate cancer during 2009 and 2010. With near-universal coverage through state health reform, the Massachusetts APCD contains detailed claims and encounter data on 98% of Massachusetts residents. This innovative linked database will be used for the following specific aims: Aim 1) To build collaborations with public and private stakeholders to use an APCD to guide health policy and payment reform. We will collaborate with the Massachusetts Executive Office of Health and Human Services (EOHHS) to build this novel population-based database. We will also work with the Massachusetts Health Quality Partners (MHQP), a non-profit organization that reports data on quality of care from provider groups, to assign patients to provider networks, 5 of which have been designated by CMS as Pioneer ACOs; MHQP will also play a key dissemination role by presenting our results from Aims 2 and 3 to stakeholders to guide their effective use of these findings. Aim 2) To assess variations in quality, costs, and outcomes of cancer care for patients with potentially curable breast, prostate, colorectal and lung cancer across provider networks. Aim 3) To assess variations in quality and costs of end-of-life care for patients with advanced cancer across provider networks. For the growing number of states that have or are developing APCDs and have access to cancer registries, this research will provide a highly innovative model for evaluating and monitoring the value of cancer care. The linked database will represent one of the most comprehensive population-based databases on cancer care in the US for persons of all ages.